I have just purchased a 2017 Jayco Starcraft 19' caravan that does not have a solar panel. It seems that the caravan battery can be charged from the car while driving, as noted in the ST-III manual. As we spend some nights not in caravan parks running on battery power, we really need to know whether the battery will be charged when we're driving to the next destination. Is there a way to determine whether the caravan battery will be charged from the car while driving? It's not easy to see the back of the ST-III box (without major work).